Prick potatoes twice with a fork both sides, place in microwave whole on High for 6 minutes. Turn over and cook for further 2 minutes on High. Peel and slice when cooled.
Heat 1tbsp butter with the olive oil in a pan and fry potatoes on a medium heat until crispy. Just before potatoes are finished, add sliced onions and fry until golden. Season with salt and pepper, set aside.
Heat remaining butter in another pan and fry mushrooms for 3 minutes, season. Add garlic, wine and fry until liquid has almost evaporated. Combine contents of both pans along with the parsley.
Fry for a few minutes, season to taste and serve hot.
TIP: Pricking potatoes with a fork before placing in microwave allows steam to escape evenly. Turning your potatoes means both sides cook evenly.